Standard OLEDs nowadays comprise an organic layer stack with at least one organic light-emitting layer arranged between two electrodes deposited on top of a substrate, typically a glass substrate, applying thin film deposition techniques. The layers between the two electrodes and the electrodes form an organic layer stack of thin layers with thicknesses in the order of several tens of nanometer to hundreds of nanometers. Together with the two electrodes, the stack of layers is denoted as functional layers stack in the following. Two different types of OLEDs can be distinguished with respect to the direction of light emission. In the so-called bottom emitters, the light leaves the OLED device through a transparent bottom electrode (usually the anode, usually made of indium-tin-oxide (ITO)) and a transparent substrate (e.g. glass) while the second electrode (typically the cathode made of aluminum) is reflective. In so-called top emitters the light leaves the OLED device through a transparent top electrode (e.g. ITO) and a transparent cover lid (e.g. glass), while a bottom electrode (e.g. aluminum or ITO in case of a reflective substrate) and/or the substrate is reflective. The cover lid is mandatory for these OLEDs in order to prevent the environment, especially moisture and oxygen, from reaching the organic layer stack. The bottom-emitting OLEDs are commonly used for illumination purposes. So-called transparent OLEDs are a combination of a bottom-emitter and a top-emitter having a transparent substrate and a transparent cover lid.
The functional layer stacks on top of a substrate required to generate light from an organic light emitting layer have to be shaped to serve different purposes like enabling electrical contacting of the electrodes, applying certain operating schemes to the functional layer stack, attaching cover lids to enclose the functional layer stack and/or to shape the light-emitting area in order to provide desired visual effects. A common way to structure OLED, especially the functional layer stack, is to apply shadow masks during the thin film deposition, e.g. evaporation. Shadow masks provide the possibility to process the functional layer stack inline depositing one layer after the other. The areas shielded by the shadow masks are not coated with the evaporated materials due to the shadowing effect of the mask resulting in a structured functional layer stack only present in non-masked areas of the substrate. In some cases, a particular designed mask is required for each layer during deposition. One major disadvantage of shadow masks is the need of one mask for each different pattern of masked areas resulting in a large number of required masks for manufacturing OLEDs with a varying pattern of non-emitting areas. This large number of masks makes the mask process very expensive. Another disadvantage of utilizing shadow masks is the limitation to shielded areas, which cannot be fully enclosed by deposited material. The shielding mask areas must be connected to the carrying mask frame resulting in an at least one small non-coated corridor across the OLED light emitting area.
The patent application US 2010/0155496 A1 discloses electrostatic spraying of a liquid from a tube on top of a substrate as an alternative maskless process to manufacture OLEDs. This technique is limited to organic polymers, which is not the preferred light emitting material for OLEDs. Small organic molecules as the organic material deliver the best OLED performance, but they have to be evaporated. It would be desirable to apply a structuring method avoiding shadow masks but enabling to apply the common, reliable manufacturing steps for OLEDs in an non-disturbed way enabling the use of well proven materials.